Initial setup: Korean community aggregator web app

- Set up Vite + React + TypeScript project
- Configure Tailwind CSS v4 with PostCSS
- Create project structure (components, types, data)
- Implement core features:
  - Header with search functionality
  - PostCard component for displaying posts
  - PostList with community filtering (전체/디씨/루리웹/아카)
  - PostModal for detailed post view
- Add mock data for 3 communities (DCInside, Ruliweb, Arcalive)
- Update README with project documentation

src/components/common/Header.tsx

@@ -0,0 +1,43 @@
+import React from 'react';
+
+interface HeaderProps {
+  onSearch: (query: string) => void;
+}
+
+const Header: React.FC<HeaderProps> = ({ onSearch }) => {
+  const [searchQuery, setSearchQuery] = React.useState('');
+
+  const handleSearch = (e: React.FormEvent) => {
+    e.preventDefault();
+    onSearch(searchQuery);
+  };
+
+  return (
+    <header className="bg-white shadow-md sticky top-0 z-10">
+      <div className="max-w-7xl mx-auto px-4 py-4">
+        <div className="flex items-center justify-between">
+          <h1 className="text-2xl font-bold text-gray-800">
+            한국 커뮤니티 애그리게이터
+          </h1>
+          <form onSubmit={handleSearch} className="flex gap-2">
+            <input
+              type="text"
+              value={searchQuery}
+              onChange={(e) => setSearchQuery(e.target.value)}
+              placeholder="게시글 검색..."
+              className="px-4 py-2 border border-gray-300 rounded-lg focus:outline-none focus:ring-2 focus:ring-blue-500"
+            />
+            <button
+              type="submit"
+              className="px-6 py-2 bg-blue-500 text-white rounded-lg hover:bg-blue-600 transition-colors"
+            >
+              검색
+            </button>
+          </form>
+        </div>
+      </div>
+    </header>
+  );
+};
+
+export default Header;